Data storage systems are arrangements of hardware and software that include one or more storage processors coupled to arrays of non-volatile storage devices, such as magnetic disk drives, electronic flash drives, and/or optical drives, for example. The storage processors service storage requests, arriving from host machines (“hosts”), which specify files or other data elements to be written, read, created, or deleted, for example. Software running on the storage processors manages incoming storage requests and performs various data processing tasks to organize and secure the data elements stored on the non-volatile storage devices.
Data storage systems often operate file systems, i.e., systems for organizing and managing files and directories on storage media. Such data storage systems may serve file systems as host-accessible objects, e.g., for use by clients, and/or may employ file systems for internal data management.
Data storage systems provision file systems with storage extents for persistently retaining file system data and metadata. Some file systems are “thickly” provisioned, meaning that a predetermined amount of storage space within a data storage system is reserved for the file system. Other file systems are “thinly” provisioned, meaning that a data storage system adds storage extents to the file system on demand, as the file system grows.